US3897374A - Nonstaining rubber - Google Patents

Abstract

A rubber composition is provided having nonstaining property containing therein 5-50 PHR of a novel nonstaining aromatic hydrocarbon process oil comprising polypropylnaphthalene. The process oil comprises polypropylnaphthalene of the general formula:

WHEREIN R is propyl group, n is an integer of 2 to 4, R'' is a hydrogen atom or a methyl group and n'' is an integer of 0 to 2, the total number of carbon atoms in the alkyl side chains being six to 13, and has an aniline point of not more than 10*C. It is suitable for the uses of light color rubber compositions with no staining and bleeding.

Description

United States Patent [191 Takahashi et al.

1 July 29,1975

1 1 NONSTAINING RUBBER [75] Inventors: Masaaki Takahashi, Tokyo; Noboru Ishizawa, Hyogo; Masazo Nishida, Osaka, all of Japan [73] Assignees: The Toyo Rubber Industry Co.,

Ltd., Osaka; Kureha Kagaku Kogyo Kabushiki Kaisha, Tokyo, both of Japan; part interest to each 22 Filed: Jan. 4, 1974 [21] Appl.No.:430,852

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 153,047, June 14,

1971, abandoned.

[30] Foreign Application Priority Data June 12, 1970 Japan 45-51196 [52] U.S. Cl 260/5; 208/14; 260/33.6 AQ; 260/668 R [51] Int. Cl C07c 15/24; C08c 11/22 [58] Field of Search 260/33.6 AQ, 668, 5; 208/14 [56] References Cited UNITED STATES PATENTS 8/l972 Mills et al. 260/33.6 AQ

OTHER PUBLICATIONS Kirk-Othmer Encyclopedia of Chemical Techn."

(2nd Ed.) (Vol. 14) (Interscience) (N.Y.) (1967), pages 849-850, 853, 854. TP9E68.

White et al., Rubber Journal, pages 50-52 and 55 (June 1966).

Primary ExaminerDonald E. Czaja Assistant ExaminerH. H. Fletcher Attorney, Agent, or Firm-Sughrue, Rothwell, Mion. Zinn & Macpeak [57] ABSTRACT A rubber composition is provided having nonstaining property containing therein 5-50 PHR of a novel nonstaining aromatic hydrocarbon process oil comprising polypropylnaphthalene.

The process oil comprises polypropylnaphthalene of the general formula:

lee

11 Claims, No Drawings l NONSTAINING RUBBER CROSS REFERENCE TO RELATED APPLICATIONS The application is a continuation-in-part application of copending application, Ser. No. 153,047, filedtlune 14, 1971, now abandoned.

BACKGROUND OF THE INVENTION plasticization effect and reduction in cost. Particularly,

and the lower the aniline point is the more increased is the staining property. g I

Thus, the rubber composition with which the present invention is concerned may be suitably used. as for ex ample, for light color rubber compositions for white ribbons of tires, or black color rubber compositions in contact with light color rubber compositions. The-compositions also have application in fields where rubber compositions compounded with a large amount of a softening agent have been believed not to be desirable. for example, in tirecarcasses, canvas shoe soles, etc. Further, it is greatly expected that the rubber compositionof this invention will be applied in new fields, such ascolored. tires or patterned tires. 7

DETAILED DESCRIPTION OF THE INVENTION 200 to 250C fraction) obtained from a raw material a large amount extending from to 50 partsby weight, per 100 parts by weight of rubber, of petroleum oil softening agent has been employed for styrenebutadiene copolymers of solution-polymerized polybutadiene.

Most of the petroleum oils which have hitherto been employed are so-called aromatic extender oils,,which may be advantageously compounded in a rubber composition in a large amount, but impart staining and light discoloring to a rubber composition.

On the other hand, naphthenic extender oils have also been employed, as less or nonstaining softening agents in rubber compositions.

The compounding amount of naphthenic oil was however, fairly limited because the compounds are likely to bleed on a surface of the rubber composition when they are used in large amounts which leads to staining of rubber. US. Pat. No. 3,681,279 discloses an attempt in the preparation of'a nonstaning oil byelimi-' arom atization for eliminating polar compounds. Therefore, the product according to the process'of this patent contains 1555% non-aromatic hydrocarbons, i.'e., sat

urated hydrocarbons. Thus, there 'is 'no'disclostire therein with respect to the fact that 100% aromatic compound is useful to achieve nonstaining properties.

The present invention has been accomplishedf to solve the prior art defects or drawbacks, as above, in

softening agents for rubber. I

SUMMARY OF THE- INVENTION According to the invention, thereis' 'thus provided a rubber composition containing therein a novel aro matic hydrocarbon process oil comprising polypropylnaphthalene, which oil has an aniline point of not more than 10C, preferably not more than 5C and exhibits no staining property when compounded with a rubber composition.

This finding is unexpected in view of conventional ideas or knowledge thatusual aromatic oilscurrently used have aniline points'ih 'a ran ge of from 25 to 40C:

for l to 0001 second, a naphthalene fraction separated from coal tar, a naphthalene fraction in a by-produced bottom oil obtained in the catalytic improvement of n h hw A The above process oil comprising polypropylnaphthalene obtained in the present invention is quite differcnt fro m", the conventional process oil generally obtained the'purifi'cation and separation of a mineral oil, That is, the process oil of the present invention contains no carbon'bonding constitutinga naphthene ring,- and is anoil fraction composed of pure aromatichydrocarbons. Therefore, the conventional. manner foranalyz ing the component (such -as-n -d"-M method, V, .G.C. method, which are calculated from the 'measurement'of physical'constants) is not applied, and it was confirmed by gas chromatography, NMR, mass-spectrum, etc., that the process oil comprises a naphthalene compound a having two to four propyl groups; such as, dipropyl-i naphthalene, tetrapropylnaphthalen'e, etc.

Isomers thereof are of course in'c-luded, but in.,the' present invention it is not necessary to separate the isomers.-Any compounds'represented by the'above general formula having a boiling point-range of 280 to- 450C can beemployed. The reason for specifying the general formula of the compounds according to-the present, invention is based on the considerations of methylnaphthalene and 'dimethylnaphthalene" 1 containediin a naphthalene fraction, and even though those; propyl compounds are contained. in the process oil-,.-. there is ,no problem in'practicing. the ,present inventionwt,

The physical propertiesof polypropylnaphthalene oil 1 of the present invention are generally as'fo'llows.

Boiling Point 3 0 400c Cminucd diffusing towards the surface of the rubber composition u g s article. Also the rubber compositions are not at all de- Roflccumcc 8 graded in mechanical properties, such as, tensile Flash Point 100C strength.

. h C 5 Moreover, it should be remarked that the rubber Pmm um I m composition or compound has good processability, for ybolt example, tackiness and adhesiveness.

000B In particular, the use of the rubber composition is eflective for the improvement in adhesion to polyester, Aniline Point not more than l0(, nvlon or Steel cord prclcrahl not more I than 5( lt was generally required that various light color or white rubber articles, for example white ribbons for Table l given below shows the performance on one tires, not only do not stain, but also can maintain their of the process oils employed in the examples of the whiteness from the viewpoint of commercial value, present invention, as compared with those of typical whereas it has been a general tendency in recently that process oils now commercially available. a large amount of a process oil is compounded with TABLE 1 Performances of Various Process Oils Process Oil Conventional Conventional Conventional Article Paraffinic Naphthenic Aromatic of the Item Oil Oil Oil Invention Specific Gravity 0.8735 0.8859 1.0065 0.9677 (d Aniline point 997 70.0 34.1 10.0 (C.)

Reflectance 1.4794 1.5068 l.57l5 1.5654 (Nll'lfl) Color (ASTMD-ISOO) l.() 3,7 3.0 l.()

VGC 0.805 01:78; 0.9561 1.082

Remark VGC (Viscosity gravity constant) 0755 In the above equation, G symbolizes the specific gravity at 60F. and V symbolizes the Saybolt universal viscosity at 2l0F.

As is apparent from Table 1 above, the process oil for use in the present invention is characterized in that its aniline point is fairly low with high aromaticity.

The rubber component, with which the process oil for use in the present invention having the above mentioned good properties may be compounded, includes any kind of elastic high polymers, such as, natural rubbers or synthetic rubbers. The synthetic rubbers are exemplified by styrene-butadiene copolymers obtained by emulsion polymerization, butadiene-acrylonitrile copolymers. polybutadiene, styrene-butadiene copolymers, obtained by solution polymerization. polybutadiene, neoprene, polyisoprene, styrene-butadiene copolymers, or butadiene-acrylonitrile copolymers. prepared by alfin catalyst polymerization.

In particular, polymers having high polarity and great cohesive energy between. main chains. for example styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, or neoprene have strong affinity for and swell readily in the process oil of the present invention so that it is possible to incorporate the process oil in the polymer in a larger amount.

The rubber compositions containing the specified process oil to which the present invention relates is nonstaining and bleeding or blooming phenomena do not tend to be caused by the process oil migrating of rubber in rubber compounding, which tendency often leads to rubber staining due to the large amount of the process oil.

In accordance with the invention, such requirement as above can be satisfied by the use of the process oil specified hereinbefore.

Thus, the rubber compound containing the particular process oil of the invention is characterized in that there is no danger that the oil either discolors a light colored compound or transfers from a black rubber compound to a light colored or white compound adjacent thereto, and, as a result, discolors the latter.

In other words, the process oil for use in the invention has substantially no bleeding nor blooming tendency and can keep a clear color.

The compounding amount of the process oil for proving the rubber compound of the present invention is suitably in a range of from 5 to 50 PHR. When the amount is less than 5 PHR, the inherent effect of the process oil on the rubber, i.e., improving processability, cannot be developed, while when the amount is in excess of 50 PHR, an adverse influence may be exerted upon the properties of the rubber itself.

In compounding operations, other usual ingredients of the rubber industry may also be incorporated as desired. Further the process oil of the invention may be used in combination with a minor proportion of a commercially available process oil.

The preparation of the rubber composition of the present invention may be accomplished, forexample, by a procedure of producing a so-called oil-extended rubber which comprises mixing the specified process oil in emulsified form with a copolymer rubberlatex. coaqulating the mixture by a salt or acid and drying the resultant rubber composition. or by an orthodox procedure by means of a mixing apparatus. such as a Banbury mixer or open mill. 1n the former procedure. it may be advantageous to further add carbon black on extending the rubber with oil to prepare a masterbatch rubber. It is to be understood that any procedure for preparing a rubber composition may be conducted.

The following examples in which, unless otherwise stated, and parts are both by weight. will illustrate the embodiments of the invention in more detail.

EXAMPLE 1 A polymer having a Mooney viscosity of 120 was prepared by the polymerization of 72% butadiene with 28% styrene at 5F using a 5% potash soap solution as emulsifier so that convention rate is 75%. To the resulting polymer latex was added and mixed thoroughly polypropylnaphthalene in an emulsified form, which polypropylnaphthalene had been prepared by cracking a petroleum oil hydrocarbon at a high temperature of l,O0OC to yield a naphthalene fraction having a boiling point range of 200 to 250C, hydrotreating the distillate in the presence of a cobaltmolybdenum catalyst and concurrently purifying it, and reacting the hydrotreated product with propylene in the presence ofa silica-aluminum catalyst. The process oil is mainly composed of tripropylnaphthalene having a boiling point range extending from 330 to 380C and an aniline point of 8C, and is hereinafter abbreviated as AX-l Here, an emulsifier comprising 2 parts of oleinic acid and 2 parts of ammonium hydroxide per 100 parts of the process oil was used for the cmulsification of the oil.

The mixture so prepared was flocculated by a salt or acid to obtain a product in small particle form, which product was then dried, milled on an open roll mill and formed into a thick sheet by a sheeting step. The thus obtained product comprised of the mixture is hereinafter abbreviated as PAX." The mixture PAX" comprises 100 parts of the polymer and 37.5 parts of the process oil and has a Mooney viscosity value of 55.

By way of comparison. a commercially available napthenic oil-extended rubber, as shown in Table 2 below, was employed as the rubber component. The thus prepared mixture PAX" (this invention) and the commercially available naphthenic oil-extended rubber (comparative) were compounded and mixed respec tively with the ingredients listed in compounding formulae of Table 2, i.e., in accordance with Compound No. 11 for the former and Compound No. l for the latter by means of Banbury mixer in which the process oil for use in the present invention (Abbr. AX-l) for the former and a commercially available naphthenic process oil (Abbr. NA) for the latter were employed respectively as softening agents. Thus, both rubber compounds were prepared. The various properties of the rubber composition, uncured, and cured, obtained in accordance with the present invention are shown in Table 3 and Table 4 in contradistinction to those of the comparative composition.

Oil-extended rubber having a Mooney viscosity value of 100C. (ML of 48 composed of a st'yrene-butadienc copolymcr rubber with a styrene content of 23.5% and 37.5 PHR of a nonstaining naphthenic process oil.

Natural Rubber Smoked Sheet No. 3.

Fast Extrusion Furnace Carbon Black Polyolefin Tackificr NA is a naphthenic process oil Sonic R-50" and AX-l is the polypropylnaphthalene of this invention.

Styrenated phenol N-cyclohexyl-Z-benzothiazolesulphenamide TABLE 3 Properties of (ireen Sheet 1 I Compound 1 Compound ll (Comparative) (This Invention) Mooney viscosity 25 26.5 (ML at 100C.)

Mooney scorch time unit rise time at 125C.) 15" 430 Strength (Kg/em") (23C.) 1.21 1.28 (speed; mm/min) (40C.) 0.52 0.85

Tackiness (Kg) (23C.) 2.32 2.01 (speed by Pick-up method: 1000 mm/min) (40C.) 1.1 1.78

TABLE 4 Properties o1 Vuleanizate* *The vulcanizate was obtained under a press vulcanization condition of 150C. for 40 minutes from the green counterpart.

A process oil was prepared by cracking crude oil at a temperature of 1,200C. to yield a naphthalene fraction having a boiling point range of 200 to 250C. hydrotreating the distillate in the presence of a cobaltmolybdenum catalyst and reacting the hydrotrcated product with propylene in the presence of silicaaluminum catalyst. The thus-obtained process oil is of polypropylnapthlene mainly composed of tripropylnaphthlene and tetrapropylnaphthlene (the weight ratio being 1:1) having a boiling point range of 35040()C. and aniline point of10.5C. and is hereinafter abbreviated as AX-2.

The rubber composition (Abbreviation: FAX-2) was prepared in a similar manner to Example 1 in accordance with the white carbon compounding formula shown in Table 5 below using the process oil (AX-2).

Compound 1 Compound ll (Comparative) (This Invention) Modulus at 300 7: elongation Kglcm 56 58 Tensile strength (Kg/Cm) 164 172 Elongation at break (7r) 550 570 Tear strength (Kg/cm) 46 54 Shore hardness v 48 4) Bound elasticity (25C.) 60 58 H-test (Kg/em) 12.5 13.8 (adhesion to nylon 1260 d/2) Contact staining property (Exposure to a weatherometer for 48 hours at C.) none none EXAMPLE 2 40 TABLE 5-Continued Remarks: *Nonstaining styrenwbutadiene copolymer having styrene content of 23.5".

By way of comparison. comparative rubber compositions (Abbreviations: PA. PB and PD) were also prepared in a similar manner to the above formula, except that a commercially available, nonstaining. naphthenic oil (Abbrv. A for PA) or a commercially available. staining aromatic oil (Abbr. B for PB) was used as the process oil instead of FAX-2 as in the present invention. and no process oil was used (for PD).

vulcanization was conducted at C. for 40 minutes.

The resultant vulcanizates were subjected to accelerated weathering tests with a weatherometer to determine discoloration degree.

The results are shown in Table 6 below.

Discolorati on degree by weatheromcter CXPOSUI'C1('% Comparative This-Inven "PA' PB 'PD FAX-2 Before exposure 83,0 83.0 84.5 85.0 After exposure 60.5 6510' magnesium oxide. of which whitenessdegree is 84.5%.

Degree of discoloration by oil shllt a 2 with a color meter to determine degree of discoloration in a similar mannerto Example :2. Y

. Thezr-esults are shown in Table 9 below; by evaluating ,from the-viewpoint. of process oil bleed. 2, 1

TABLE 9 (71 weathcro meter CXPOSUI'C ICSI. J A I 1 PaAx-z PPA.. PPB PPD 's'etsrg reassure so so so so The process oils of this invention and the oomparat. tives, the same as those used in Example 2, were compared with each other with regard to discoloration by oil bleed.

First. orr p n ing l k rub r omp n (PPA. As is apparent from the results, the rubber composiwere pr p r pecti ly m th tion of the present invention has a markedly superior process oils (A, B, AX-2) in accordance with the comnonstaining property, as well as physical properties to pounding formula shown in Table 7 below. those of prior art rubber compositions.

Also, the black compound with no process oil was While the invention has been described in detail and prepared (PPD). with reference to specific embodiments thereof. it will Further, a white rubber compound was prepared acbe apparent to one skilled in the art that various cording to the compounding formula as shown in Table changes and modifications can be made therein with- 8 below (PW). out departing from the sprit and scope thereof.

Then the white compound in sheet form having a What is claimed is: thickness of ca.l mm was superimposed on each of the .30 1. A rubber composition containing therein 5-50 black compounds in sheet form and vulcanized at parts by weight per I00 parts by weight of a rubber 145C. for 40 minutes. component, of a nonstaining aromatic hydrocarbon oil Thus, the corresponding composite vulcanizates which consists essentially of polypropylnaphthalene of were obtained. the general formula,

TABLE 7 Black Compound (parts by weight) PPA PPB PPD PPAX-Z SBR-l502 100 I00 l00 100 FEF Carbon black 50 50 50 Zinc oxide 3.5 3.5 3.5 3.5 Stearic acid L5 L5 1.5 1.5 Antioxidant (WS) 10 1.0 1.0 1.0 Accelerator (CZ) 1.2 L2 1.2 L2 9071 non-soluble sulfur 2.2 2.2 2.2 2.2 Picopale 100-SF 3.0 3.0 3.0 3.0 Process oil A B AX-2 TABLE 8 r g Rn White Compound (parts by weight) 35s No. l (NR) l0().0

inc oxide 7.0

Titanium Oxide (Tim white) 401) wherein R rs propyl group, n is an integer of 2 to R Calcium carbonate (Hakuenka CC) 20.0 is a hydrogen atom or a methyl group and n is an integer of l and 2, the total number of carbon atoms is the Microcystallinc w 5: alkyl side chains being six to l3, and said oil having an Coumaron resin 20 Accelerator MSA L2 aniline point of not more than 10 C and a boiling point non-soluble sulfur 1.0 ranging from 280 to 450 C 65 2. A rubber composition as claimed in claim 1,

Thereafter the vulcanized composite article irradiated by light on the white part thereof was measured wherein the amount of said nonstaining aromatic hydrocarbon oil is in a range of 10 to 25 parts by weight per parts by weight of the rubber component.

3. A rubber composition as claimed in claim I, wherein said aniline point is nottmore than C.

4. A rubber composition as claimed in claim I, wherein said aromatic hydrocarbon oil has a boiling point in the range of 300-40()C.

5. A rubber composition as claimed in claim I. wherein said polypropylnaphthalene is tripropylnaphthalene.

6. A rubber composition as claimed in claim 5, wherein said polypropylnaphthalene is a mixture of triand tetrapropylnaphthalene.

7. A rubber composition as claimed in claim I, wherein the rubber component is a high polarity rubber having high cohesive energy between molecules selectcd from the group consisting of styrenebutadiene copolymer, butadiene-acrylonitrile copolymer, neoprene and blends thereof with other polymers.

8. A rubber composition as claimed in claim 7, wherein the rubber component is a styrene-butadiene copolymer or a blend thereof consisting of a major proportion of styrene-butadiene copolymer and a minor proportion of natural rubber.

9. A rubber composition as claimed in claim 1, which contains therein a white reinforcing agent.

I0. A rubber composition as claimed in claim l, wherein said polypropylnaphthalene is obtained by treating naphthalene or a naphthalene fraction having a boiling point of 200 to 250C with propylene.

II. A rubber composition as claimed in claim I. wherein said nonstaining aromatic hydrocarbon oil consists of said polypropylnaphthalene of said general formula.

Claims (11)

1. A RUBBER COMPOSITION CONTAINING THEREIN 5-50 PARTS BY WEIGHT PER 100 PARTS BY WEIGHTOF RUBBER COMPONENT, OF A NONSTANDING AROMATIC HYDROCARBON OIL WHICH CONSISTS ESSENTIALLY OF POLYPROPYLINAPHTHALENE OF THE GENERAL FORMULA,

2. A rubber composition as claimed in claim 1, wherein the amount of said nonstaining aromatic hydrocarbon oil is in a range of 10 to 25 parts by weight per 100 parts by weight of the rubber component.

3. A rubber composition as claimed in claim 1, wherein said aniline point is not more than -5*C.

4. A rubber composition as claimed in claim 1, wherein said aromatic hydrocarbon oil has a boiling point in the range of 300*-400*C.

5. A rubber composition as claimed in claim 1, wherein said polypropylnaphthalene is tripropylnaphthalene.

6. A rubber composition as claimed in claim 5, wherein said polypropylnaphthalene is a mixture of tri- and tetrapropylnaphthalene.

7. A rubber composition as claimed in claim 1, wherein the rubber component is a high polarity rubber having high cohesive energy between molecules selected from the group consisting of styrenebutadiene copolymer, butadiene-acrylonitrile copolymer, neoprene and blends thereof with other polymers.

8. A rubber composition as claimed in claim 7, wherein the rubber component is a styrene-butadiene copolymer or a blend thereof consisting of a major proportion of styrene-butadiene copolymer and a minor proportion of natural rubber.

9. A rubber composition as claimed in claim 1, which contains therein a white reinforcing agent.

10. A rubber composition as claimed in claim 1, wherein said polypropylnaphthalene is obtained by treating naphthalene or a naphthalene fraction having a boiling point of 200* to 250*C with propylene.

11. A rubber composition as claimed in claim 1, wherein said nonstaining aromatic hydrocarbon oil consists of said polypropylnaphthalene of said general formula.